In a magneto ignition system of the inductive type, permanent magnets are usually mounted in the rim of the flywheel. During the starting of the engine, it is possible for the engine to "kick-back" if insufficient energy is expended to start it in the normal direction and it is possible that it may be rotated in the reverse direction and voltage pulses might be developed which would sustain reverse engine operation. In certain applications, such as chain saws, this can be an extremely hazardous condition. While the system embodying this invention does not prevent primary current from flowing in the primary coil circuit, it does prevent the switching transistor from interrupting such primary current flow and thereby inhibit the generation of an ignition pulse which would cause engine operation in the event of reverse magneto rotation.
U.S. Pat. No. 4,401,096 discloses a control network to prevent reverse rotation of an internal combustion engine. In this patent, the circuit designed to prevent anti-reverse running is combined with the basic timing control circuit of the system. The combination circuit includes two R/C time delay networks which, in forward flywheel rotation, establish the firing point of the ignition system and for reverse rotation, prevent ignition by premature firing of a control transistor. The drawback of this combined arrangement is that it involves a critical timing relationship which requires accurate selection of the values of the two R/C time delay networks.
In the system embodying this invention, an anti-reverse running circuit is provided which is separate and distinct from the control circuit and does not modify the normal operation of the timing control circuit.
The system is thus very reliable in operation and avoids the criticality of attempting to counterbalance the operation of a pair of R/C networks, as in the prior art.
It is the principal object of this invention to provide an improved inductive ignition system having a reliable anti-reverse running feature.
It is a further object of this invention to provide an inductive ignition system of the above type which overcomes the drawbacks of the prior art.